/*
* Allocates memory and sets *pbufout to point to it. The memory
* contains the code table.
*/
static int
write_code_table_to_memory(buf_cache *pc,
SymbolEncoder *se,
uint32_t symbol_count)
{
uint32_t i, count = 0;
/* Determine the number of entries in se. */
for(i = 0; i < MAX_SYMBOLS; ++i)
{
if((*se)[i])
++count;
}
/* Write the number of entries in network byte order. */
i = htonl(count);
if(write_cache(pc, &i, sizeof(i)))
return 1;
/* Write the number of bytes that will be encoded. */
symbol_count = htonl(symbol_count);
if(write_cache(pc, &symbol_count, sizeof(symbol_count)))
return 1;
/* Write the entries. */
for(i = 0; i < MAX_SYMBOLS; ++i)
{
huffman_code *p = (*se)[i];
if(p)
{
unsigned int numbytes;
/* The value of i is < MAX_SYMBOLS (256), so it can
be stored in an unsigned char. */
unsigned char uc = (unsigned char)i;
/* Write the 1 byte symbol. */
if(write_cache(pc, &uc, sizeof(uc)))
return 1;
/* Write the 1 byte code bit length. */
uc = (unsigned char)p->numbits;
if(write_cache(pc, &uc, sizeof(uc)))
return 1;
/* Write the code bytes. */
numbytes = numbytes_from_numbits(p->numbits);
if(write_cache(pc, p->bits, numbytes))
return 1;
}
}
return 0;
}
/*
* Write the huffman code table. The format is:
* 4 byte code count in network byte order.
* 4 byte number of bytes encoded
* (if you decode the data, you should get this number of bytes)
* code1
* ...
* codeN, where N is the count read at the begginning of the file.
* Each codeI has the following format:
* 1 byte symbol, 1 byte code bit length, code bytes.
* Each entry has numbytes_from_numbits code bytes.
* The last byte of each code may have extra bits, if the number of
* bits in the code is not a multiple of 8.
*/
static int
write_code_table(FILE* out, SymbolEncoder *se, uint32_t symbol_count)
{
uint32_t i, count = 0;
/* Determine the number of entries in se. */
for(i = 0; i < MAX_SYMBOLS; ++i)
{
if((*se)[i])
++count;
}
/* Write the number of entries in network byte order. */
i = htonl(count);
if(fwrite(&i, sizeof(i), 1, out) != 1)
return 1;
/* Write the number of bytes that will be encoded. */
symbol_count = htonl(symbol_count);
if(fwrite(&symbol_count, sizeof(symbol_count), 1, out) != 1)
return 1;
/* Write the entries. */
for(i = 0; i < MAX_SYMBOLS; ++i)
{
huffman_code *p = (*se)[i];
if(p)
{
unsigned int numbytes;
/* Write the 1 byte symbol. */
fputc((unsigned char)i, out);
/* Write the 1 byte code bit length. */
fputc(p->numbits, out);
/* Write the code bytes. */
numbytes = numbytes_from_numbits(p->numbits);
if(fwrite(p->bits, 1, numbytes, out) != numbytes)
return 1;
}
}
return 0;
}
static void
reverse_bits(unsigned char* bits, unsigned long numbits)
{
unsigned long numbytes = numbytes_from_numbits(numbits);
unsigned char *tmp =
(unsigned char*)alloca(numbytes);
unsigned long curbit;
long curbyte = 0;
memset(tmp, 0, numbytes);
for(curbit = 0; curbit < numbits; ++curbit)
{
unsigned int bitpos = curbit % 8;
if(curbit > 0 && curbit % 8 == 0)
++curbyte;
tmp[curbyte] |= (get_bit(bits, numbits - curbit - 1) << bitpos);
}
memcpy(bits, tmp, numbytes);
}
static huffman_node*
read_code_table_from_memory(const unsigned char* bufin,
unsigned int bufinlen,
unsigned int *pindex,
uint32_t *pDataBytes)
{
huffman_node *root = new_nonleaf_node(0, NULL, NULL);
uint32_t count;
/* Read the number of entries.
(it is stored in network byte order). */
if(memread(bufin, bufinlen, pindex, &count, sizeof(count)))
{
free_huffman_tree(root);
return NULL;
}
count = ntohl(count);
/* Read the number of data bytes this encoding represents. */
if(memread(bufin, bufinlen, pindex, pDataBytes, sizeof(*pDataBytes)))
{
free_huffman_tree(root);
return NULL;
}
*pDataBytes = ntohl(*pDataBytes);
/* Read the entries. */
while(count-- > 0)
{
unsigned int curbit;
unsigned char symbol;
unsigned char numbits;
unsigned char numbytes;
unsigned char *bytes;
huffman_node *p = root;
if(memread(bufin, bufinlen, pindex, &symbol, sizeof(symbol)))
{
free_huffman_tree(root);
return NULL;
}
if(memread(bufin, bufinlen, pindex, &numbits, sizeof(numbits)))
{
free_huffman_tree(root);
return NULL;
}
numbytes = (unsigned char)numbytes_from_numbits(numbits);
bytes = (unsigned char*)malloc(numbytes);
if(memread(bufin, bufinlen, pindex, bytes, numbytes))
{
free(bytes);
free_huffman_tree(root);
return NULL;
}
/*
* Add the entry to the Huffman tree. The value
* of the current bit is used switch between
* zero and one child nodes in the tree. New nodes
* are added as needed in the tree.
*/
for(curbit = 0; curbit < numbits; ++curbit)
{
if(get_bit(bytes, curbit))
{
if(p->one == NULL)
{
p->one = curbit == (unsigned char)(numbits - 1)
? new_leaf_node(symbol)
: new_nonleaf_node(0, NULL, NULL);
p->one->parent = p;
}
p = p->one;
}
else
{
if(p->zero == NULL)
{
p->zero = curbit == (unsigned char)(numbits - 1)
? new_leaf_node(symbol)
: new_nonleaf_node(0, NULL, NULL);
p->zero->parent = p;
}
p = p->zero;
}
}
free(bytes);
}
return root;
}
/*
* read_code_table builds a Huffman tree from the code
* in the in file. This function returns NULL on error.
* The returned value should be freed with free_huffman_tree.
*/
static huffman_node*
read_code_table(FILE* in, unsigned int *pDataBytes)
{
huffman_node *root = new_nonleaf_node(0, NULL, NULL);
unsigned int count;
/* Read the number of entries.
(it is stored in network byte order). */
if(fread(&count, sizeof(count), 1, in) != 1)
{
free_huffman_tree(root);
return NULL;
}
count = ntohl(count);
/* Read the number of data bytes this encoding represents. */
if(fread(pDataBytes, sizeof(*pDataBytes), 1, in) != 1)
{
free_huffman_tree(root);
return NULL;
}
*pDataBytes = ntohl(*pDataBytes);
/* Read the entries. */
while(count-- > 0)
{
int c;
unsigned int curbit;
unsigned char symbol;
unsigned char numbits;
unsigned char numbytes;
unsigned char *bytes;
huffman_node *p = root;
if((c = fgetc(in)) == EOF)
{
free_huffman_tree(root);
return NULL;
}
symbol = (unsigned char)c;
if((c = fgetc(in)) == EOF)
{
free_huffman_tree(root);
return NULL;
}
numbits = (unsigned char)c;
numbytes = (unsigned char)numbytes_from_numbits(numbits);
bytes = (unsigned char*)malloc(numbytes);
if(fread(bytes, 1, numbytes, in) != numbytes)
{
free(bytes);
free_huffman_tree(root);
return NULL;
}
/*
* Add the entry to the Huffman tree. The value
* of the current bit is used switch between
* zero and one child nodes in the tree. New nodes
* are added as needed in the tree.
*/
for(curbit = 0; curbit < numbits; ++curbit)
{
if(get_bit(bytes, curbit))
{
if(p->one == NULL)
{
p->one = curbit == (unsigned char)(numbits - 1)
? new_leaf_node(symbol)
: new_nonleaf_node(0, NULL, NULL);
p->one->parent = p;
}
p = p->one;
}
else
{
if(p->zero == NULL)
{
p->zero = curbit == (unsigned char)(numbits - 1)
? new_leaf_node(symbol)
: new_nonleaf_node(0, NULL, NULL);
p->zero->parent = p;
}
p = p->zero;
}
}
free(bytes);
}
return root;
}
///////////////////////////////////////////////////////////////////////////////
// Builds a Huffman tree from the data in the in file.
// Returns nullptr on error.
// The returned value should be freed with free_huffman_tree.
HuffmanNode* readCodeTable(Stream& in, uint32_t& dataBytes)
{
if(!readHeader(in))
{
fprintf(stdout, "Error: wrong file signature.\n");
return nullptr;
}
HuffmanNode* root = new HuffmanNode(NON_LEAF);
bool bOk = true;
uint32_t nbEntries = in.read( );
dataBytes = in.read( );
while(nbEntries-- > 0)
{
// [ symbol ] [ number of bits ] [ count of this symbol (# instances ]
HuffmanNode* p = root;
const Symbol symbol = in.readSymbol();
const Byte numbits = in.readByte();
const uint32_t count = in.read();
std::string s;
if(in.inError())
{
bOk = false;
break;
}
// note that the bytes are padded. For exameple,
// if a symbol takes 11bits, code will read 2 Bytes
Byte numbytes = (Byte)numbytes_from_numbits(numbits);
Byte* bytes = (Byte*)malloc(numbytes);
// read the actual bytes
if(in.read(bytes, numbytes))
{
// Adds the entry to the Huffman tree. The value of the current bit
// is used switch between zero and one child nodes in the tree.
// New nodes are added as needed in the tree.
for(unsigned int curbit=0; curbit<numbits; ++curbit)
{
unsigned char bit = get_bit(bytes, curbit);
p = p->getSubNode(bit, curbit, symbol, count, numbits);
s += bit ? "1" : "0";
}
//fprintf(stdout, "symbol: %03d, nbBits: %02d, %03d, nbEntries:%d %s %p %p\n", (int)symbol, (int)numbits, (int)numbytes, (int)nbEntries, s.c_str(),
// root->one(), root->zero());
}
else
{
bOk = false;
free(bytes);
break;
}
free(bytes);
}
if(!bOk)
{
fprintf(stdout, "Cannot read table\n");
delete root;
root = nullptr;
}
return root;
}
size_t HuffmanCode::nbByte( )const
{
return numbytes_from_numbits(m_nbBits);
}
